In biological and chemical assays, such as protein crystallisation, variables such as buffer composition, concentration, pH and the nature of chemical additives, often need to be screened and controlled. In recent years assays have been performed in a parallel manner. For example, an assay is automated and performed on a two-dimensional array of analyte samples such that data is acquired at the same time from the analyte samples in the array. This reduces the time and costs involved in such assays.
In protein crystallisation, crystallisation conditions for a given protein can be optimised by investigating the parameter space defined by temperature, pH, ionic strength and additional agents. Normally investigations involve dispensing a crystallisation solution into a container, sealing the container and incubating the contained solution for a period of, typically, one week to three months. During this period the contained solution is inspected, e.g. under the microscope, for formation of crystals. Clearly such investigations can be exhaustive and thus make the process repetitive and time-consuming. Thus, performing the investigations in a parallel manner can reduce the time and cost involved.
A number of incubators with a temperature control facility have been reported. Such incubators can be used for protein crystallisation investigations. In one example, the incubator has an aluminium plate, such as a microtiter plate, which defines an array of wells that are configured to receive protein in solution. In use, hot and/or cold water is circulated around the plate to control the temperature of protein solution held in the plate.
WO 03/080900 describes a system for growing crystals, such as protein crystals. The system has an array of wells or channels defined in a substrate which are configured to receive a crystallisation solution. Associated with the array of wells or channels is a temperature controller for creating a temperature differential across the array.
It has been appreciated that proper temperature management during protein crystallisation assays can prevent the breakdown of valuable analyte material, can increase the reproducibility of experimental results and can aid in the discovery of fresh parameters that hitherto could not be investigated. However, proper temperature management of assays performed in a parallel manner has hitherto proved difficult.
It is an object of the invention to provide a method of and apparatus for incubating analyte, e.g. for the purpose of protein crystallisation.